Aircraft compass



Oct. 11, 1938. K. E. KUNZE ET A1. 2,132,740

- AIRCRAFT COMPASS I Filed Sept. 4, 1956 INVENTORS Patented Oct. 11, 1938 1 L r UNITED era-res PATENT OFFICE f 2,132,740 j p e AIRCRAFT COMPASS ."Kar'olus E. -Kunze, 'Ja maicaQN. Y., and Theodore L. Son-H00, Quincy, Mass.

Application September 4, 1936, Serial No. 99,380 4 Claims. (01. 33-222) The invention relates to aircraft direction inunderstood thatthe design of this case and such struments in which a. 'gyroscopically stabilized details as methods of preventing pivots fror'h magnetic field having radial horizontal =compopermanently leaving their jewels are omitted as nents maintains a system of directive and stabibeing non-pertinent.

V 5 lizing magnets in the horizontal plane, the mag- A directive magnet I, Figs. 1 and 2, is fastened 5.-

net system being mounted in approximately to frame 4 by means of'a 'suspender wire'5; Two neutral gravitational suspension. The object of auxiliary magnets 2, 2; Figs. 1 3, are also the invention is to allowtheuse of statically balsecured to frame 4 by Suspender wires "5. Each anced magnetic directive systems thereby proof these three magnets, I, 2, and'2, is placed'with l0 viding magnetic direction instruments free from its poles t n qual distances from the pivot errors due to accelerating the instruments. point. The like poles of these three'magn'ets are As is well known, the present magnetic dir'C- adjacent. In this case "the :three south seeking tion instruments necessarily use gravitationally poles are located nearest pivot '3. The mag-net 'l' pendulous' directive elements since any indicating is placed with its axis in a plane which contains l5 device, such as a card or filament, attached to a the card meridian and which is normalto the 1 5 non-pendulous directive element may assume p ne of t ed O he h d- Magnets 2 practically an azimuth orientation without deplaced symm t y relative t ma t n stroying the alignment between the resultant this case the magnets 2., 2 are placed with their magnetic axis of the system and the external axes in a plane which contains the card east field. In other words, when a non-pendulous a w st p ntsandth ax s e p As 20 directive system is perfectly balanced about its wn in t d e axes o "t three center of rotation, the indicator completely loses magnets, s @9759, he a Plane p p its directive qualities; v I lar to the geometrical axis of the pivot 3, and

The improvements described herein permit the slig y be w e p i of t e a eruse of non-pendulous magnetic directive systems A ma s n, attached to frame byte euspehdel 25 with the consequent freeing of the instruments wire 5, balances the weight of magnet -l. from the adverse efiects of accelerations. The magnet System here including the These improvements are applicable to sev ral card, is statically balanced relative to the point types of magnetic direction instruments such as of pivot 3. This is done in any desirable manner.

the aperiodic compass; the card compass; opti- In this case the final adiustment'of the vertical 3-0 cally read compasses, etc, but only one such apposition of the 'center of mass is made by raising plication is hereindescribed. This is a cardl We the P P t by Sc wtype compass employing the improvements i ing this pivot in oro'utof its threaded holder. question. It is illustrated by the accompanying In Summary, the magnetic directive System drawing in which'Fig. 1 is a plan view of the spesists f a directive magnet having one p at; cific instrument chosen for illustration; Fig, 2 is farther from the center of rotation than the a sectional elevation on the meridian plane; Fig. other; tWO auxiliary magnets having their pol s 3 is a sectional elevation on the east-west vertical sym e ri a ly o at d r ativ to t dire tiv plane; 'Fig. 4 is a schematicdiag'ram of t t magnet but withthe poles of each at unequald-is=- 40 bilizing magnetic field; d Fig 5 is a diagram tances from the center of rotation, like poles of 40; showing the torques acting on a portio of th the three magnets lying adjacent to each other; directive system, in a vertical plane through the a frame holding the three s in fi ed DOSi center of motion, V I tion relative to each other; an adjustable pivot Fig. 1 shows a normal side-reading card 6 car yi hi fr m a b n in ma ried by a frame 4 which is attached to the pivot and a pas d attached t e frame 45, 3, thelatter being vertically adjustable relative to fixed position relative to the magnets. t entire the frame. This is shown in Figs. 2 d 3 system being adjusted to neutral mass balance Where the pivot is' se'en to be threaded and relative 13017118 pivot point. 7 screwed through a sleeve which forms the center AS e w t three magnets are of equal of frame 4. The pivot '3 rests upon a normal- Size and all like poles are at equal distances from 50 type jewel 1, Figs. 2 and 3,'which is held inthe he center of rotati n.

top of a post 8. The post is secured to the bot- A circular spool [2, Figs. 1, 2, and 3, is mounted tom of a case indicated fragmentally at 9. .An in a fixed position on three struts, II, which are index M is mounted immovably, relative to the secured to the case 9. The spool i2 is located e for reading the card. 1tis,of course tube concentrically with a line Vi W c pa s. 56

generally, through the point of pivot 3. This line,

VV, is normally a true vertical, and is perpendicular to the plane of the spool I2. Two grooves are turned in the rim of I2 and in these grooves two coils of insulated wire, I3 and I4 Figs. 2 and 3, are placed. The windings are, therefore, short solenoids having the common axis VV. Nonpertinent detail such as coil terminals, leadouts,

etc., is omitted. When in circuit with a battery or other source of electrical energy, not shown, the coils are so connected that current traverses the upper coil, I3, in the clockwise direction asplane. The point C represents the center'of the magnetic field created by these coils. The plane H--H is parallel to the planes of coils I3 and I4; lies midway between these planes; and. passes through C.

Current through I3 (Fig. 4). is in. the direction indicated, and .in the reverse direction through I4, as shown. The resulting magnetic field is represented by the circular fiux lines 5, as shown.

Points m, q, and t represent positions of a north-seeking pole placed in the field. The forces with which the resultant field due to coils I3 and I4 acts upon this north-seeking pole, in the three positions, are representedby the vectors f2, 1, and f1. r

In Fig. 5 the outer tip of magnet I is sketched in the field justconsidered. Thisview is also taken on a vertical planethrough the center of the field, C, the cutting plane also containing the center of rotation Q, of the magnet system.

With the north-seeking pole in the position a, Fig. 5, intermediate between the points q and t, Fig. 4, the forcefri, due to the field of coils I3 and I4, acts upon it. Simultaneously, the earths magnetic field actsupon this pole with the force F. The resultant of the two forces in and F is represented by the vector R1.

Similarly, if the pole n is rotatedabout Q to a position b (i. e., to the region m, Fig. 4) the coil field vector frZ and the earths field vector act upon the pole n with the resultant force R1.

It is evident that the magnet pole n, in position a, develops a clockwise torque R1 d1 about the center of rotation, Q,- while the counter-clockwise torque R2 d2 acts, about Q, when the pole n' is in position b. The factors d1 and (12 are th torque arms, as is apparent.

' Similar, but generally oppositely directed torques about Q are developed by the action of the resultant forces upon the south-seeking pole, s, when the latter lies near the center of rotation, Q, as is the case with the magnets I, 2, and 2, Figs. 1, 2, and 3. However, these torques are always less than those due to the north-seeking pole, n, because of the reduced coil field near C and, also, because of decreased torque arms. For purposes of qualitative explanation the torques due to the south-seeking pole may, therefore, be neglected.

From the foregoing, the

duced:

, 1. Considering the magnet I Figs. 1 and 2, the vertical equilibrium position of the pole n will lie between two such positions as a and b, Fig. 5, With the strength of the field due to coils I3 and I4 several times that of the earths field, and

following may be dewith the point of pivot 3, Figs. 2 and 3, near the plane of symmetry of the field (i. e., Q near C, Fig. 5), the pointsa and b will lie close together and the rest point for the pole n will be close to the plane I-IH regardless of the azimuth position of n. a

2. The line VV is perpendicular to the plane HI-I. Since VV is also the axis of the solenoidal windings which give rise to the forces 11, f2, the components of the latter which are parallel to I-I--I-I intersect V-V. This line, V--V is a true vertical when the instrument functions (see following). For these reasons the coil-field vectors"(f1 acting upon any magnet in the field, give rise to no torques about VV. Bccause of this, the horizontal component of the earths field acting upon the directive magnet I,

1 Figs. 1 and 2, provides the usual directive torques about the point of pivot 3.

3. The resultant torques due to the action of the earths field on the two auxiliary magnets 2, 2, Figs. land 3, are zero because of the symmetrical positions of. these magnets relative to the center of rotation.

The resultant field of coils I3 and I4, acting upon'the magnets 2,'produces no torque about VV for the reason discussed in 2, above.

In the case of these auxiliary magnets it will be noted that the two outer, n, poles must lie either in theplane H1-I or at unequal distances therefrom. When one of these n poles is above the plane I-I H while the other is below, it is evident from a study of Figs. 4 and 5 that a torque which tends to restore both n poles to the plane H-H is set up. Actually, this restoring torque comes into play whenever the two 12 poles of these auxiliary magnets 2 are not at equal distances from the plane HH.

In other words, the total effect of the two auxiliary magnets 2, 2 is to maintain the east-west axis of the directive element parallel to the plane HH.

4. As a result of considerations 1, 2, and 3,

7 above, it is evident that the plane determined by the three outer, or n, poles of the magnets I, 2, and 2, Figs. 1, 2, and 3, will be maintained in practical parallelism with the plane H-H, Figs. 4 and 5, whenever the coils I3 and I4 are prop erly'energized. At the same time an unimpeded directive effort is developed by the magnet system, due to the action of the horizontal component of the earths field on the directive magnet, I, when the plane I-I--H is horizontal. This plane HH is maintained in the horizontal position by gyroscopic stabilization, as will be explained, the coils I3 and I4 being pendulously mounted within the aircraft.

The results obtained from the entire system are, then, as follows: 7

The directive element, being in neutral mass balance relative to its center of motion, is unaffected by the inertia torques which act when the system is accelerated. This directive element is held nearly in the horizontal plane by the com-- bined action of the gyroscopically stabilized ring magnetic field, produced by the coils I3 and I4, and, the three magnets I, 2, and 2. The magnet I, being asymmetrically placed, reacts with the earths magnetic field and provides a directive torque, that is, a torque which orients the directive element, relative to the magnetic meridian.

One form of the detailed arrangement of the gyroscopic stabilizer is that shown in the draw- The compass case 9 is mounted upon the .top of a vertical ring l5, Figs. 2 and 3, while the gyro. case 3|, 39 'issecured to the bottom of this ring,

as shown. v

The entire instrument is carried by a pivot H. which is mounted in a sleeve. 18, this sleeve being rigidly fastened to the top of the inner rim of ringl'5. A cup bearing 2|, Figs. 2 and 3, carries'the pivot I! and, hence,.the entire instrument, This cup bearing, is mounted ina holder 22 which is fastened to a bar 23. The bar 23 terminates in a bracket 24 drilled, as indicated, for mounting in the aircraft.

The bar 23 has two openings, 25 and 26 Figs. 1 and 2, cut through it for the purpose of allow-v ing clearance for the ring l when the bar 23 assumes various angles relative to thevertical. line V-V. As actually constructed, the bar 23 is built up of several pieces in order to allow the no rotation relative-to the bar 23.

ring l5 and its azimuth guide (see following) to beplaced in position, but for the purpose of simplifying the explanation it is shown as a single unit in the drawing.

The azimuth guide referred to above consists of the two rollers, 21, 21 Figs. 1, 2, andB, which are mounted in a small gimbal ring 29, by means of the pivots 28. Thus each roller, 21, may rotate, within the ring 29, upon an, axis determined by the center line of its pivots, 28. The gimbal ring 29 is, itself, mounted upon two pivots, 3H, 3,6, which may rotate in bearing holes formed in bar 23 at the ends of the opening 26. The axis of pivots 30 is parallelto the axes of pivots 28 and passes through the point of pivot IT. The rollers 21 bear lightly against the sides of ring I5, when the instrument is assembled, as shown in the drawing.

This arrangement allows the ring I5 and, hence, the entire instrument, complete freedom of rotation about the point of pivot I1, except in azimuth. In azimuth, the ring l5 and, therefore, the entire instrument, is restrained, and allowed Thus the compass case 9 and the index 4| are maintained in an invariant azimuth position relative to the aircraft. At the same time, the pitching and rolling motions of the aircraft are transmitted to the instrument only by the friction at the point of pivot '11 and by the friction of the azimuth guide pivots 28, 30, L The latter is very small due to the negligible pressures involved in the operation of the azimuth guide.

We consider this type of suspension to be very desirable, as it does away with the usual multiplebearing gimbal system.

The bottom of ring I5 is fastened, as previously mentioned, to the top of the upper portion, 3|, of the gyro rotor case, Figs. 1, 2, and 3. This case is completed by the lower portion, 39, screwed into position on 3| as shown. A boss in the upper center of the case holds a bearing 34, while a bearing 35 is similarly mounted in a boss in the lower part of the case. The rotor axle 36 spins in these two bearings. A conventional air-driven impulse wheel 31, mounted upon the axle 36. forms the gyro rotor. The blades are indicated at 38. The driving air jet is formed, in the usual manner, by the aspiration of the rotor case and the use of a nozzle 40, Figs. 1 and 2, at the case opening.

The aspiration of the case is effected, in this instance, by connecting the vacuum line to the instrument by means of a short flexible coupling, not shown, connected to the tube 20. The tube 20 is secured to the pivot I! as shown in Fig. 3,

the purpose of this arrangement being to place the instrument terminus of the flexible coupling as near the center of relative motion as possible. This. obviates, to a large extent, deflecting torques dueto the coupling. The air flow between rotor case and flexible coupling is through the air ducts 33 and32, Fig. 2, in the upper case 3|, thence through the ducts I6 in the ring I5, and thence through the ducts l9, in sleeve I8 and pivot 11, tothe tube 20... The ring I5 is an assembly because of the constructional requirements in forming the ducts l6.

The spinv axis of the rotor 31 passes through the points of pivots l1 and 3 and thus coincides with the instrument vertical, VV.

The center of mass of the entire system lies in the line VV and at a distance from the point of pivot I1 which is determined by the required period of oscillation of the system about this point.

The complete action has been described, but may be summarized as follows:

The. magnetic axis of the directive element, mounted in neutral mass suspension, is constrained to lie very nearly in the horizontal plane, andin the plane of the magnetic meridian, by the combined action of. the earths magnetic field and ag-yroscopically stabilized external magnetic field. The vectors defining the external field intersect the vertical line through the center of mo tion of the directive element. The resultant of the earths field and the external field also pro duces torques, by interaction with the poles of auxiliary stabilizing magnets, which disappear only when the east-west axis of the directive element lies in the horizontal plane, the torques always movingthis axis toward the horizontal. No directive, or azimuth, torques result from the interaction of. thefields and the auxiliary magnets.

It is to be noted that the method of creating the external stabilizingfield is not confined to 3, might be placed at a considerable distance from each other, l3 being at the top of the case 9 and i4 being near the bottom. That is, the distances 1/, and 1J2, Fig. 4, may be varied at will.

Detail in arrangement may also vary to any extent. For instance, the single directive magnet may be replaced by a system of directive magnets, and similarly for the auxiliary magnets. The latter may be located at positions other than those shown herein. The spool i2, Figs. 1, 2, and 3, may be external to the case 9 and gyroscopically stabilized, alone. The entire case 9 is herein shown stabilized only for purposes of description.

It is also to be understood that we do not limit the arrangement herein described to any particular type of instrument. The card-type of compass has been described, but the principle is fully applicable to aperiodic compasses; optical1y-read compasses; remote reading, or remote indicating compasses; etc.

We are well aware of the prior design of neutrally'balanced magnetic directive elements; of gyroscopically stabilized double-pivoted magnetic compasses; etc., but we believe the combination of neutrally balanced directive element having magnets arranged as described, stabilizing external field, and gyroscopic stabilization for the external field, forms a new and useful prin- 1. In an aircraft instrument, the combination of a frame; a vertically adjustable pivot supporting said frame; a directive magnet attached to said frame with its poles at unequal distances from the point of said pivot; auxiliary magnets attached to said frame, each having its poles at unequal distances from the point of said pivot, but the auxiliary magnets being symmetrically and immovably arranged relative to said directive magnet and the axis of said pivot, said directive and auxiliary magnets having like poles adjacent; a supporting bearing for said pivot; means for mounting said bearing in an aircraft; means for creating a stabilizing magnetic field around said directive and auxilary magnets, said field being such that it possesses a plane of magnetic symmetry and that all vectors defining said field intersect a particular normal to said plane of magnetic symmetry, said particular normal intersecting said plane of symmetry at the center of the stabilizing field and determining with each field vector a plane perpendicular to said plane of symmetry, the said vectors having components normal to, and directed either toward or away from said plane of magnetic symmetry, for all points of the effective field outside of said plane; means for pendulously supporting, within the aircraft, the said means for creating the stabilizing field; and gyroscopic means for stabilizing said supporting means for maintaining the said plane of magnetic symmetry in a nearly horizontal position.

2. In an aircraft magnetic instrument of the character described in this specification, the combination of means for creating a stabilizing magnetic field around the directive element, said means consisting of two solenoids having a common axis assing through the center of motion of the directive element and energized by electric currents which rotate clockwise in one solenoid and counterclockwise in the other solenoid, the two solenoids being placed above and below, respectively, a normally horizontal dividing plane; and gyroscopic means for maintaining the said means for creating the stabilizng field in position with the solenoidal axis of the stabilizing magnetic field in a vertical position, regardless of motion of the aircraft.

3. In an aircraft magnetic direction instrument, the combination of a magnetic directive element; means for producing, around the directive element, a stabilizing magnetic field of the type described in this specification; a mounting, containing air ducts, for said means for producing the stabilizing field; a single hollow pivot attached to said mounting; a gyro case attached to 'said mounting; a support holding a bearing for said hollow pivot; a gimbal ring; means for mounting said gimbal ring in said support for rotation about a normally horizontal axis passing through the point of said hollow pivot; two spaced guide rollers; means for mounting said rollers in said gimbal ring for rotation about axes parallel to the axis of rotation of said gimbal ring; a circular guide member, arranged to slide between said spaced rollers; means for fastening said guide member, immovably, to said mounting, concentrically relative to the point of said hollow pivot; a tube attached to said hollow pivot and connecting with the interior thereof; and air ducts connecting the interior of said hollow pivot to the interior of said gyro case whereby air may be exhausted from-said case to spin the gyro.

4. Inan aircraft instrument of the type described in this specification, the combination of a pivotally mounted neutrally-balanced, magnetic compass directive element having a directive magnet placed entirely on one side of the center and auxiliary magnets, offset from the center and placed in symmetricalangular relationship relative to the directive magnet and on opposite sides of same, substantially as described; and two solenoids having a common axis passing through the pivot point of said magnetic directive element, the said two solenoids being arranged to carry electric currents in relatively opposed rotary senses, and being placed one above and one below a normally horizontal plane passing through, or close to, the point of pivotal mounting of said magnetic element, and whereby the axes of the said directive and auxiliary magnets are constrained to lie nearly parallel to said plane of symmetry while the directive force of said magnetic directive element is unaltered by the magnetic field of said solenoids.

KAROLUS E. KUNZE. THEODORE L. SOO-HOO. 

